Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$45.38	7.482%	$48.7753	$48.78	$48.80	$48.80
Purchase #2	$37.39	3.582%	$38.7293	$38.73	$38.75	$38.70
Purchase #3	$88.47	3.335%	$91.4205	$91.42	$91.40	$91.40
Purchase #4	$198.77	11.774%	$222.1732	$222.17	$222.15	$222.20
Purchase #5	$76.75	11.133%	$85.2946	$85.29	$85.30	$85.30
Purchase #6	$207.71	4.636%	$217.3394	$217.34	$217.35	$217.30
Purchase #7	$21.75	3.227%	$22.4519	$22.45	$22.45	$22.50
7 purchase totals =	$676.22		$726.1842	$726.18	$726.20	$726.20